Due to advantages such as high energy density, high average open circuit voltage and long cycle life and the like, Li-ion batteries have been widely applied in mobile and portable electrical appliances. The electrode of a commercialized Li-ion battery includes a current collector, an electrode tab and an active material layer, the active material layer is a continuous and uniform coating layer. A cathode electrode, an anode electrode and a separator together form a cell, and the thickness of the cell is the sum of the thickness of the cathode electrode, the thickness of the anode electrode, the thickness of the separator and the thickness of the electrode tab. Different portions of the cell have different thicknesses, and the portion where the electrode tab is welded has the maximum thickness. With respect to commercialized Li-ion batteries, the thickness of the model of batteries is generally defined according to the maximum thickness of the battery.
Since electronic products are developing to be smarter and multifunctional, requirements on the energy density of the Li-ion batteries are becoming higher and higher. Therefore, the battery needs to contribute a larger capacity within the same space. With respect to the traditional Li-ion battery, the thickness thereof is accumulated based on the thickness of the electrode tab, such that the thickness of the area where the electrode tab is welded is the maximum thickness of the battery, and the thickness of the area where no electrode tab is welded is relatively smaller. However, the space thereof cannot be fully utilized. As a result, within a specific range of models and sizes, it is hard to further improve the capacity of the battery. Accumulation of the thickness of the electrode tab to the thickness of the battery has become a bottleneck in further improvement of the energy density of the traditional Li-ion battery.
The cell of a conventional Li-ion battery is subjected to accumulation of thickness to the electrode cell by the electrode tab and the insulating adhesive, such that the electrode tab area is the area where the thickness of the battery is the maximum, and the space of the cell outside the electrode tab area is wasted, leading to a loss of energy density. Although the energy density loss may be improved by means of designing an electrode tab accommodating groove, the electrode tab accommodating groove contributes no energy, and the problem of accumulation of thickness caused by the insulating adhesive adhered on the electrode is not solved, thereby affecting sufficient improvement of the energy density.
In the related art, a groove is provided on the electrode, and the electrode tab is welded in the groove, so as to improve energy density. Chinese Patent Application CN 203733894 U has disclosed a Li-ion battery, in which a first groove is arranged on a cathode diaphragm, a second groove is arranged on an anode diaphragm, a cathode electrode tab is welded in the first groove, and an anode electrode tab is welded in the second groove; upper and lower surfaces of the cathode electrode tab are coated with a first insulating adhesive layer, and the surface of the cathode diaphragm corresponding to the second groove is coated with a second insulating adhesive layer. Since the active material layer is removed from the first groove and the second groove, thus no energy contribution is made in this region. In addition, the insulating adhesive layer also occupies a part of the space inside the battery, thereby affecting sufficient improvement of the energy density.
In view of the above defects in the related art, the present application is proposed.